Thread: timing question...

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Newly built motor....496 c.i., Dart 310 heads, 14:1 (approx.)....cam is .725 lift, 282 / 292 dur. @ .050. 110 lobe sep.. I ran this motor twice, and was a little disappointed with the performance. Disassembled, and found the cam was initially set @ 8 degrees retarded(??). The cam mfg. was a little puzzled, to say the least. The motor ran well....meaning that the rpm was close to 8000 at the end of the 1/4 mile, but didn't make the h.p. I expected. Why was this done? I'm in the process of doing a makeover....having the heads ported, and intend to degree the cam. I'm going to re use this cam, because the mfg. says it's ideal for the application. I'm planning on changing the initial timing to 6 degrees advanced. Any input on this will be appreciated, as always. Thanks.

no i do not think your cam is ideal for your application ?? but you did not say what you have this 496 in. car /whats the weigth and how much stall or stick ? .what type intake what is the make ? . how big of carb ? what size headers . in short heads may be fine for alower rpm and the cam not so much .need more input on your build .what ET are your trying to get to??? 282/292 @ 050 ? with 700 less lash. weres the head flow at 700 ? so your going to put the cam in at 104 intake center line ? that could help some pull the cam coming in at a lower rpm should help out of the hole not sure if i would cut up a set of heads if the cams wrong in the first place. you may find the cam was moved for lack of piston to valve room if this cam is this big @ 050 you have no PV move the cam check intake valve you may find out why it was moved

Thanks for the reply....the car is 3400 w/ driver, 4.10 gear, p/g 5500 stall, super victor intake w/ 1200 cfm Quick Fuel Dominator, fenderwell headers w/ 2" primary tubes. After headwork, heads flow 320 @ 700 lift. I made 2 passes with motor, before heads were done, and cam installed as stated. Both passes were 10.20's @ 130 mph, 7800 rpm. I suspected insufficient power, due to low mph. The car ran 10.40's @ 133 mph with everything else the same, except small block motor.....same rpm (7800). I think the car should be in the high to mid 9's @ 136 - 140 mph.

to much cam less rpms work on TQ or bigger heads more rpms= HP them heads flow 320 cfms? seams abit low you need more 375-400cfms. headers are abit small .i would be building a set of step tubes to 2.1/8 to 2.1/4 or just 2.250 .1200 cfm is more then you need right now if you pushing pass 7800 you heads are not going to cut it more cam lift hi 700s i not sure i would build a small bore engine the way your going at it with a 4.250 crank and hi rpm s every thing works better with a bigger bore .why do you want to run this engine so hi in RPMs? any thing past 7500 your beating up valve springs every thing need to be right try putting the cam were it needs to be first ?

and I'll bet his trans is overheating!!!!

If he has lost 3 mph at same rpm-----the big block is slushing the box the trans came in

Originally Posted by jerry clayton

and I'll bet his trans is overheating!!!!

If he has lost 3 mph at same rpm-----the big block is slushing the box the trans came in

5500 stall 7800+ thu the big end needs a very good oil pan with some oil controll oil pan big bore less crank killer set of heads big cam . good valve train... and then come off the line just be for the valve springs flatten out all kidding a side the stall could be going away heads are to small for 8000

I suspected the heads and possibly the trans after making a couple passes.....that's why I tore the motor down. I might have given you the wrong info on the heads. After the porting job, I was told they flow better than Dart Pro 1 320's. Actually,320 is the runner size, on the heads. I'm told they will be good to 750-800 h.p. I'm really starting to second guess the use of this cam, based on your input.....which is contrary to tech support at Lunati. After talking to the previous owner / builder of this motor, I would guess the cam was set @ 8 degrees retarded for exhaust valve clearance. Rather than keep it that way, I'm probably going to replace it with something a little better suited to the motor. I know a bigger cube motor would help the situation, but I bought this one with new rotating assembly, so I would like to keep it where it is. It should still be capable of 750 h.p., don't you think? The reason for the choice of cam was probably because it was originally built to go in an 1800 lb. roadster. Like I said....the trans will be completely different the next time this car runs, but the #'s I posted were with the TH400 that was used behind the small block...with the same convertor.

smaller cam then i built or help in bulids were we used abit less cam @050.save them big number cams for very hi rpm engine or big cid . some thing very lite that cam may work better. some were in the 268 to 273 on it may be on a 108 with a 400 trans the bbc like to be short shifted .not so much the cid the bigger bore make the heads work better. try to like the rpm down abit .